n. a tumour composed of a number of tissues that are not usually found at that site and are derived from all three embryonic germ layers. Teratomas most frequently occur in the testis and ovary (see dermoid cyst), possibly derived from remnants of embryonic cells that have the ability to differentiate into many types of tissue; in most malignant teratomas, cells from all three germ layers are present. Malignant teratoma of the testis is found in young men: it is more common in patients with a history of undescended testis. Like seminoma, it frequently occurs as a painless swelling of one testis (pain is not a good indication that the swelling is benign). Treatment is by orchidectomy avoiding an incision into the scrotum. The tumour can spread to lymph nodes, lungs, and bone, treatment of which may involve the use of chemotherapy drugs, such as vinblastine, bleomycin, cisplatin, and etoposide, with a high cure rate even in metastatic disease.
Teratomas often produce alpha-fetoprotein, beta human chorionic gonadotrophin, or both; the presence of these substances (tumour markers) in the blood is a useful indication of the amount of tumour and the effect of treatment.
Subjects: Medicine and Health.